Fluid digital positioner



July 2, 1968 R. w. WARREN 3,390,611

FLUID DIGITAL POSITIONER Filed Nov. 25, 1966 2 Sheets-Sheet 1 July 2,1968 R. w. WARREN 3,390,611

FLUID DIGITAL POSITIONER Filed Nov. 25, 1966 2 Sheets-Sheet BIAS CONTROLVENT OUTLET BLEED OUTLET FEEDBACK CONTROL 206 SET SHOCK LOCATION SETPRESSURE I42 CLOSE FIG. 3

INVENTOR RAYMOND w. WARREN ATTORNEYS United States Patent 3,390,611FLUID DIGITAL POSITIONER Raymond W. Warren, McLean, Va., assignor to theUnited States of America as represented by the Secretary of the ArmyFiled Nov. 25, 1966, Ser. No. 597,148 9 Claims. (Cl. 91-3) Thisinvention relates to a fluid digital positioner and more particularly toa digital positioner which is variably positioned in response toswitching of one or more of a plurality of bleed type, bistable wallinteraction ampliiers.

Digital positioners have long incorporated fluidic means for variablypositioning the same. All known fluid operated, digital positionersemploy movable valve members and other elements which tend to affect thereliability of operation and at the same time increase the response timeof the positioner.

It is, therefore, a primary object of the present invention to provide afluid operated digital positioner which is extremely simple and reliableand yet able to produce sophisticated control functions.

It is a further object of this invention to provide a fluid digitalpositioner whose position is controlled by a plurality of fluidamplifiers of the bistable type.

It is a further object of this invention to provide an improved fluiddigital positioner which is characterized by the absence of movingparts.

Other objects of this invention will be pointed out in the followingdetailed description and claims and illustrated in the accompanyingdrawings which disclose, by way of example, the principle of thisinvention and the best modes which have been contemplated of applyingthat principle.

In the drawings:

FIGURE 1 is a schematic, elevational view of one form of the fluiddigital positioner of the present invention.

FIGURE 2 is a schematic, elevational view of the fluid digitalpositioner shown in FIGURE 1 after switching of one of the bistablefluid amplifiers providing the fluid input to the positioner.

FIGURE 3 is a schematic view of a second embodiment of the fluid digitalpositioner of the present invention as applied to the sensing of a shockwave within a compressible high velocity fluid.

In general, the invention is directed to a digital fluid positionersystem which includes a casing forming a closed fluid working chamberincluding a wall member carried thereby and movable longitudinallytherein. A plurality of bistable fluid amplifiers are provided whichinclude plural power stream outlets. Means are provided for coupling atleast one outlet of each fluid amplifier to the working chamber atpoints spaced longitudinally along the casing. Means are furtherprovided for biasing the movable wall to a first position within thecasing. Digital fluid input means selectively switch the fluidamplifiers whereby the movable wall member shifts longitudinally from afirst position to a second position to maintain a like number of fluidamplifiers delivering to and receiving fluid from the working chamber.

In one form, the wall member separates the closed easing into opposedfluid working chambers. Both outlets of each fluid amplifier are coupledto the casing on opposite sides of the casing center line such that whenthe movable wall member is centrally positioned within the casing, oneamplifier outlet is carrying fluid flow to one working chamber, whilereceiving fluid from the second working chamber.

In a second embodiment, only one outlet of each amplifier is coupled tothe elongated casing. The second outlet of each fluid amplifier acts asa bleed and means are pro- 3,398,611 Patented July 2, 1968 ice vided fornormally biasing the amplifier power stream to the bleed outlet. Theamplifier fluid outlets each connected to the casing are selectivelycoupled to a working chamher while the other working chamber receivesbiasing fluid to set the positioner wall member at an initial position.

Referring to FIGURE 1, there is shown schematically a plurality of fluidamplifiers 10, 20, 3t), 40 and 50 for controlling the position of thefluid positioner. The amplifiers are of the bistable, bleed, wallinteraction type which feed fluid into and receive fluid from a closedelongated casing 60, in the form of a cylinder. Casing 60 carriesinternally, a piston 62, which is slidable longitudinally of thecylinder. In this regard, the piston 62 has coupled thereto an axiallyextending piston rod 64 extending outwardly of left-hand and right-handends 66 and 68. Appropriate apertures 70, carried by the end walls 66and 68, allow the rod 64 to slide therethrough, being fluid sealed withrespect to the casing end walls.

The fluid amplifiers are all identical; for instance, fluid amplifier 10includes a power stream inlet port 12 for directing the power streamselectively through interaction chamber 14 to left and right-handoutlets 16 and 18 under normal bistable operation. Left and hight-handcontrol ports 22 and 24 control which fluid outlet receives the powerstream. In this case, left-hand control port 22, being last pulsed,causes the power stream to pass through outlet 18 in the directionindicated by the arrows. The right-hand amplifier outlet 18 is fluidcoupled to working chamber 28 by port 26. The piston 62 divides thecasing interior into right-hand working chamber 28 and a lefthandworking chamber 32. Each fluid amplifier is provided with appropriateleft and right-hand bleeds; for instance, amplifier 10 includes aleft-hand bleed 34 and right-hand bleed 36. In this regard, under theconditions shown in FIGURE 1, fluid is being removed from lefthandworking chamber 32 through fluid outlet connection 38, the fluidreturning to fluid amplifier 10 and passing out through bleed 34.

The remaining fluid amplifiers are identically connected to the cylinder60. The power stream for each amplifier may be selectively passedthrough either amplifier right or left-hand outlets. For instance, fluidamplifier 20 has its power stream exiting through fluid outlet 42 and bymeans of cylinder port 44 enters the right-hand working chamber 28. Theleft-hand fluid outlet 46 for the same amplifier receives fluid fromleft-hand working chamber 32 through casing port 48, the return fluidexiting through bleed 52. For fluid amplifier 30, the power streampasses from the amplifier through lefthand outlet 54 and entersleft-hand working chamber 32 through port 56. Return fluid passes fromright-hand working chamber 28 through port 58 to fluid outlet 72 at theright-hand bleed 74. All casing ports are in line, but spacedlongitudinally along the casing wall.

Fluid amplifier 40 delivers its power stream through left-hand outlet 76to the left-hand working chamber 32 through port 78. On the oppositeside of the positioner piston 62, chamber 28 delivers fluid through port80 and right-hand amplifier outlet 82 to the right-hand bleed 84. Again,with regard to fluid amplifier 50, the power stream exits from theamplifier interaction chamber through lefthand amplifier outlet 86 andeasing port 88 to the lefthand working chamber 32. Unlike the previousamplifiers, port 90 acts to fluid couple amplifier outlet 92 such thatfluid from the same working chamber 32 exits through amplifier 50 bymeans of amplifier port 92 and bleed 94.

In the operation of the fluid digital positioner, the piston 62 alwaystries to move so that the flow in and the flow out to respective workingchambers on each side of the piston are equal. Thus, for left-handpositioner chamber 32, flow enters the chamber through positioner ports56, 78 and 88 and leaves the left-hand chamber through spaced positionerports 38, 48 and 96. On the right-hand side of the piston within workingchamber 28, fluid enters the extreme right-hand ports 26 and 44 andexits to the fluid amplifiers through ports 58 and 80. Obviously, ifboth outputs of an amplifier are on the same side of the piston,switching from one outlet to the other does not affect the pistonposition. This may be readily seen when viewing FIGURE 1, in thatassuming bistable amplifier 50 switches, the power stream from theamplifier will then pass through right-hand fluid outlet 92, and port96) into the left-hand chamber 32 and out of port 88, through amplifieroutlet 86 to the left-hand bleed This Will, of course, not affect theratio of inlets to outlets for the left-hand working chamber 32 and thepiston 62 will remain in the position shown in FIGURE 1. Only thebistable amplifiers that have an output on both sides of the pistonaffect the system while in the amplifiers that have both outputs on thesame side of the system cancel themselves.

Referring to FIGURE 2, the positioner is shown under conditions in whichan amplifier having outlets on both sides of the piston, has its powerstream switched from one amplifier outlet to the other. Under theconditions shown, fluid amplifiers 1t), 30, 40 and 50 remain unswitchedwhile amplifier 20 switches. The power stream of amplifier 20 now passesthrough amplifier outlet 46 and enters right-hand working chamber 32through port 48. Since the power stream is passing through left-handoutlet 46, right-hand outlet 42 acts as a fluid return for right-handchamber 23, fluid passing through cylinder port 44 through outlet 42 tothe right-hand bleed 98. Assuming instantaneously that piston 62 is inthe same position as under the conditions of FIGURE 1, it is noted thatwithin the left-hand working chamber 32, fluid is moving into theworking chamber through ports 48, 56, 78 and 88, while fluid is exitingfrom the chamber through ports 9:), 38 and 98. Likewise, on the oppositeside of the piston within working chamber 28, fluid is entering thechamber through the extreme right-hand port 26 and is passing from thechamber to respective fluid amplifiers through ports 44, 58 and 80.Since the piston 62 always tries to move so that the flow in and out ofeach side of the piston is equal, the piston 62 will move as indicatedby the arrow 109 to the dotted line position 62. In this position, thereare on the left-hand side of the piston within working chamber 32, alike number of ports receiving fluid as those allowing fluid todischarge from the chamber. Ports 48, 56, 78 and 88 are dischargingfluid into the chamber, while ports 38, 90, 80 and 58 are receivingfluid and returning the same to respective amplifiers for dischargethrough associated bleed ports. On the right-hand side of the chamber,port 26 allows a single fluid stream to enter from fluid amplifier whilefluid is being discharged from the right-hand working chamber 28 throughport 44 to fluid amplifier bleed 98 of fluid amplifier 20.

From the above, it is obvious that if the positioning sequence isoperated from the end of the cylinder 60 toward the center, the pistonwill move each time a bistable fluid amplifier or element is flipped.

While the invention has been shown as applied to fluid amplifiers inschematic form, the fluid amplifiers themselves may be conventionallybuilt of stacked sheets including outer, imperforate sheets acting tosandwich an inner sheet, incorporating by molding or etching, therequired geometry to form the interaction chamber for each amplifier andthe multiple fluid passages or channels. The exact manner in which theamplifier is assembled through the use of the multiple plates and itsmode of connection to the elongated casing or cylinder 60 forming amajor element of the digital positioner does not form a part of thisinvention and any conventional technique may be utilized. The inventionhas equal application to pure fluid amplifiers or to fluid amplifierswhich include moving elements.

The embodiment shown in FIGURES l and 2 constitutes an extremelysimplified system in which the fluid positioner itself comprises apiston movable longitudinally within a cylindrical casing with opposedforces acting upon the piston in the form of right-hand and lef handworking chambers. The dual outlets of each amplifier are normallyconnected to associated, opposed chambers. Fluid passes from theamplifier to one chamber and is received by the amplifier from the otherchamber and discharges through an adjoining bleed. Reference to FIG- URE3 shows a second embodiment of the invention in which there is provideda single working chamber connected to the fluid amplifier. The workingchamber acts against a set biasing force which has an equal and oppcsiteeffect upon the movable wall or piston member. The piston will remain ina desired set position in the absence of an unlike number of fluid inletand outlet connections to the amplifier, in like manner to the operationof the first embodiment.

Specifically, the multi-step fluid digital positioner is employed inconjunction with a shock wave sensor to maintain the position of theshock wave at a desired position with respect to a fluid flow diffuser.It is noted that spaced members 162 and 104 define a flow path for acompressible fluid moving at high velocity and in the direction shown byarrow 1%. A shock wave 188 is created between the spaced members. Thevelocity of the fluid to the left of the shock wave is less than Mach 1while that to the right is greater than Mach 1. In this case, thepressure of high velocity fluid to the left is of higher pressure thanthe fluid to the right of shock wave. The fluid positioner in thisembodiment may, therefore,

' be used to control the position of the shock wave at 108 within thediffuser, such as normally present in supersonic aircraft.

The flueric shock positioner control system may be so designed as tomaintain a given shock position by controlling, through the use ofvents, the diffuser back pressure. Basically, the system operates byusing the change in pressure across the shock wave 1% to trigger theseries of fluid amplifiers identified from left to right as 110, 112,114, 116, 118 and 120. The number of amplifiers actuated corresponds tothe axial location of the shock wave. The total output of the amplifiersis used to move the piston 122 of the fluid digital positioner. Thepiston displacement, a direct function of shock wave position, controlsengine bleed flow and pressure and, therefore, shock location. In theembodiment shown, the piston 122 always tries to assume a positionwherein an equal number of amplifiers acting as sensors discharging outof the driving side of the piston as are discharging into the drivingside.

In this respect, the positioner casing member is provided with anenlarged bore section 124 which receives piston 122 having an enlargeddiameter wall section 126 in the order of the diameter of bore 124. Areduced diameter section 128 immediately to the left acts in conjunctionwith end wall 130 to define a fluid working chamber 132 which may beselectively coupled to a single outlet from each fluid amplifier throughslide valve 210. The reduced diameter piston section 128 is hollow todefine a bias chamber 134 which receives a set fluid pressure throughline 136 acting as indicated by arrows 138 On the forward wall 140against the pressurized fluid within working chamber 132. The fluidWithin chamber 132 acts on the annular wall 142 of the piston, asindicated by arrows 144. Movement of piston members 122 to the lefttends to close pressure relief doors (not shown) downstream of the shockwave 108. Likewise, movement of the piston 122 to the right tends toopen the relief doors.

The sensors are of the identical Wall attachment pure fluid, bistableacting type as shown in the FIGURE 1 embodiment, or alternatively, mayinclude moving parts if desired. The fluid amplifiers must act asbistable switches in response to digital pulse input. All of the fluidamplifiers are the same. For instance, the left-hand fluid amplifier |1includes a power stream inlet port 150 delivering fluid selectively toleft-hand amplifier outlet 152 or right-hand amplifier outlet 154depending upon which control nozzle 156 or 158 has last been pulsed. Apair of left and right-hand ports 160 and 162 are provided. Theright-hand port 162 acts normally as the bias control means formaintaining power stream flow through left-hand vent outlet 152 in theabsence of a pressure differential across associated left and right-handcontrol nozzles 156 and 158.

*For each of the fluid amplifiers 110, 1112, etc., there are providedcommon control nozzle connections which open up at spaced points alongthe outer surface of flow defining duct means 104. The spaced controlnozzle connections are identified as 16 4, 166, 168, 170, 172, 174, and176, respectively, from left to right.

Feedback control is provided for each fluid amplifier by means of afluid connection between the right-hand power stream outlet of oneamplifier and a left-hand port of the fluid amplifier to the left ordownstream of that amplifier. For instance, the left-hand feedbackcontrol port 160 of amplifier 110 is connected to right-hand powerstream outlets =19t of amplifier 112 by feedback channel 224. Likewise,feedback channel 222 connects the righthand power stream outlet 194 'ofamplifier 114 to the left-hand feedback control port of amplifier 112. Afluid connection 228 couples right-hand power stream outlet 198 ofamplifier 116 to left-hand feedback control port of amplifier 1 14.Feedback channels 230 and 232 function in like manner for amplifiers 118and 120, respectively.

Each amplifier includes a curved bleed outlet such as outlet 151 foramplifier 110. For the other amplifiers, from left to right, bleedoutlets 153, 155, 157, 159 and '161 are provided, respectively.

Unlike the previous embodiment, both of the power stream outlets of eachamplifier are not connected to opposed working chambers of the digitalpositioner itself, but in each case the left-hand power stream outletfor each amplifier acts as a vent. In addition to vent 152 for amplifier110, there is provided vent 178 for amplifier -112, vent 180 foramplifier 114, vent 182 for amplifier 116, vent 184 for amplifier 118and vent 186 for amplifier 120. The right-hand outlet of each fluidamplifier is coupled to slide valve 21%)- at spaced longitudinal points.

The fluid digital positioning system employs movable slide valve 210 toselectively provide an initial set shock location. The function of theslide valve 219 is to fluid couple the ports 188, 1 92, 196, etc., andassociated amplifier outlets carried thereby, to fixed ports 212, 214,2'16, 218, 220 and 222 which open up into bore 124 of easing member 100.Assuming, for instance, that the slide valve 210 is positioned as shown,ports 18-8 and 212 are in line and the right-hand fluid amplifier outlet154 is fluid coupled directly to the working chamber 132.

In operation, assuming that the shock wave 108 is initially in theposition shown, it will be seen that the pressure differential acrossthe control nozzle for amplifiers 1'10 and 112 is such that it willovercome the bias supplied to right-hand ports of these amplifiers tocause the power stream to switch from asociated vents 152 and 178 toright-band power outlets 154 and 190, respectively. Flow then passes, asindicated, through right-hand power stream outlets to the associatedports 188 and 192 carried by the slide valve 210 and through ports 212and 214 carried by the positioner casing to allow pressure flow from thefluid amplifiers 110 and 11-12 into amplifier chamber 132. The fluidpressure, of course, acts against the biasing pressure within biaschamber 134. Under the operating principles of the instant invention,the piston 122 must move to the left until it uncovers a like number ofamplifier fluid ports which will carry flow from the positioner workingchamber 132 to the amplifiers as ports which are delivering their powerstreams to the positioner working chamber. In this case, sinceamplifiers 119 and 112 are delivering flow to the working chamber 132,the next upstream amplifiers 1 14 and 116 act to receive flow from theworking chamber and discharge it through their right-hand bleeds. Inthis case, once the piston 122 has moved to the left to uncover workingchambers 216 and 218, it will stay in the position shown until there isa shift in the position of shock wave 108.

If now, the shock wave shifts to the right, so as to create a fluidpressure differential across sensing channels 168 and 170, the purefluid amplifier 114 will switch in like manner to amplifiers and 112.The power stream is no longer directed to vent 180 but passes throughamplifier outlet 1% and associated ports 1'96 and 216 such that therewill be an imbalance in the number of fluid inlet connections and outletconnections between the amplifiers and the chamber. Piston 122 movesfurther to the right. Instantaneously, ports 212, 214 and 216 will allbe delivering fluid to the chamber and only port 21-8 will be directingfluid from the chamber to fluid amplifier 116. Necessarily, piston 122must move to its extreme right position such that ports 22% and 222 willjoin .port 218 in delivering fluid from the working chamber 132 to theextreme right-hand amplifiers 118 and It is, therefore, seen that duringthe operation, as the normal shock moves, the difference in pressure onthe control ports will flip the bistable elements. If the movement ofthe shock is in the direction to retract the piston, that is, it isupstream, the difference in pressure due to the shock on the controlchannel for respective amplifiers flips each bistable element to theinternal working surface of the piston. This retracts the piston againstthe said pressure until the piston uncovers the port to the adjacentbistable element. Flow out of the working chamber and through the bleedof the adjacent bistable element balances the internal pressure againstsaid pressure and the piston is positioned at that particular port. Thepiston always positions itself so that inflow and outflow balance thesaid pressure in like manner to the embodiment of FIGURE 1. The slidevalve 210 provides the manual control of the position of the normalshock at which the relief doors (not shown) start to open.

If a digital fluid positioner of the type shown in FIG- URE 3 isemployed in a shock wave sensing environment, the switching of anintermediate fluid amplifier without first switching the otheramplifiers to the left thereof will have the effect of automaticallyswitching all of the amplifiers to the left. The feedback control willact in opposition to the original bias and cause the power stream of theamplifiers to the left to switch from the left-hand vent outlets to theright-hand power stream outlets directing fluid to the positionerworking chamber.

Again, in the second embodiment, the invention has been shown inschematic form. However, it is readily apparent that the pure fluidamplifiers themselves, as well as the digital positioner and itsassociated slide valve, are formed in conventional fashion. The specificstructure of the amplifiers or the digital fluid positioner form no partof the present invention.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in theform and details may be made therein without departing from the spiritand scope of the invention.

What is claimed is:

1. A fluid positioning system comprising a casing forming an enclosedfluid working chamber including a wall member movable longitudinallythereof, a plurality of bistable fluid amplifiers each having pluralpower stream outlets, means for coupling at least one outlet of eachfluid amplifier to said working chamber at points spaced longitudinallyalong said casing, means for biasing said movable Wall to a firstposition within said casing, and

means for selectively switching said fluid amplifiers whereby saidmovable wall member moves longitudinally from said first position to asecond position to maintain a like number of fluid amplifiers deliveringto and receiving fluid from said working chamber.

2. The system as claimed in claim 1 wherein each fluid amplifierincludes bleed means for allowing fluid passing from said workingchamber to said amplifier to be bled from said amplifier, While saidamplifier power stream passes through said other amplifier outlet.

3. The system as claimed in claim 1 wherein each fluid amplifier has asingle amplifier outlet coupled to said working chamber and said systemfurther includes means for normally biasing said fluid amplifier powerstream to said outlet not connected to said working chamber.

4. The system as claimed in claim 2 further including feedback meanscoupling a power stream outlet of one amplifier and a port associatedwith another fluid amplifier to effect automatic switching of a secondamplifier in response to switching of said first amplifier.

5. The system as claimed in claim 1 wherein said means for coupling atleast one outlet of each fluid amplifier to said working chamber atpoints spaced longitudinally of said casing includes an intermediateslide valve for selectively coupling said amplifier power stream outletsat various longitudinal positions along said casing.

6. The system as claimed in claim 1 wherein said means for biasing saidmovable wall to a first position comprises a second working chamber onthe opposite side of said wall and acting in opposition to said firstWorking chamber, and outlets of each fluid amplifier are coupled torespective working chambers when said wall is centered with respect tosaid casing.

7. A digital fluid positioner system comprising a closed, elongatedcasing carrying a longitudinally movable wall member acting to separatethe casing into opposed fluid working chambers, a plurality of bistablefluid amplifiers, each having a pair of fluid outlets, the fluid outletsfor each amplifier being coupled to the casing at longitudinally spacedpositions on opposite sides of said movable Wall member when said wallmember is positioned centrally of said casing, and means for selectivelyswitching said fluid amplifiers whereby said movable wall member seeks aposition longitudinally within said casing such that each workingchamber has the same number of fluid outlets passing power stream fluidfrom said working chamber to said amplifiers as outlets delivering powerstream fluid from the fluid amplifiers to the chamber itself.

8. The system as claimed in claim 7 wherein each fluid amplifierincludes bleed means associated with each amplifier outlet, downstreamof the power stream inlet to the amplifier, whereby power stream fluidreturning from one working chamber through said amplifier outlet may bebled from the amplifier without affecting power stream flow from saidamplifier to said other working chamber through said other amplifieroutlet.

9. The system as claimed in claim 7 further including opposed controlports carried by each fluid amplifier on opposite sides of said powerstream and each of said control ports adapted to pulse said power streamin response to digital input signals to efiectively switch said powerstream from said one amplifier outlet to said other amplifier outlet.

References Cited UNITED STATES PATENTS 3,181,546 5/1965 Boothe l3781.53,248,053 4/1966 Phillips l37-8l.5 X

MARTIN P. SCHWADRON, Primary Examiner. C. B. DORITY, 111., AssistantExaminer.

7. A DIGITAL FLUID POSITIONER SYSTEM COMPRISING A CLOSED, ELONGATEDCASING CARRYING A LONGITUDINALLY MOVABLE WALL MEMBER ACTING TO SEPARATETHE CASING INTO OPPOSED FLUID WORKING CHAMBERS, A PLURALITY OF BISTABLEFLUID AMPLIFIERS, EACH HAVING A PAIR OF FLUID OUTLETS, THE FLUID OUTLETSFOR EACH AMPLIFIER BEING COUPLED TO THE CASING AT LONGITUDINALLY SPACEDPOSITIONS ON OPPOSITE SIDES OF SAID MOVABLE WALL MEMBER WHEN SAID WALLMEMBER IS POSITIONED CANTRALLY OF SAID CASING, AND MEANS FOR SELECTIVELYSWITCHING SAID FLUID AMPLIFIERS WHEREBY SAID MOVABLE WALL MEMBER SEEKS APOSITION LONGITUDINALLY WITHIN SAID CASING SUCH THAT EACH WORKINGCHAMBER HAS THE SAME NUMBER OF FLUID OUTLETS PASSING POWER STREAM FLUIDFROM SAID WORKING CHAMBER TO SAID AMPLIFIERS AS OUTLETS DELIVERING POWERSTREAM FLUID FROM THE FLUID AMPLIFIERS TO THE CHAMBER ITSELF.